For example, to evaluate , after ( has been pasted in the entry line, enter

One may also use the
alpha key to enter the index as i or k as used more often in summation
notation. For example, to compute the sum of as k goes from 1 to 100, first select 4:( sum from the Calc menu. Then, after ( has been pasted in the entry line, enter

K K

To
evaluate ,
after ( has
been pasted in the entry line, enter

K K N

The TI-89 can evaluate some basic infinite
series, such as . After ( has been pasted in the entry line, enter

K K ) ENTER

Solve

You can easily solve equations using the TI-89 graphing calculator.
The key decision for user is whether to work in the real or the complex
number system. For example, let's solve the quadratic equation, .

To solve the equation in the real number system, press F2 to select
the algebra menu, press 1 to select 1:solve(, enter the equation,
then press , (comma) X ) ENTER. The TI-89 responds with the
answer false, indicating that this equation has no real roots.

To obtain the complex roots, follow the above procedure with the
following exception. Instead of selecting 1:solve( , select
A:Complex , then select
1:cSolve. The complex roots are

In particular, note that the option 1:solve yields solutions only in
the real number system; whereas, cSolve yields solutions in the complex
number system.

You may also solve an equation with a constraint. This is handy, for
example, in solving trigonometric equations. For example, letŐs solve
) = 1 for . The appropriate syntax is:

solve(equation,variable) | constraint.

Here, the entry line is

solve(sin(2x)=1,x) |

Consult the test menu for details on how
to enter inequalities and the "and".